Bio-based epoxy resin based on 4-propyl guaiacol as well as preparation method, degradation method, reprocessing method and application of bio-based epoxy resin

Abstract

The invention provides bio-based epoxy resin based on 4-propyl guaiacol as well as preparation, degradation and reprocessing methods and application of the bio-based epoxy resin, and relates to the technical field of epoxy resin. The bio-based epoxy resin based on the 4-propyl guaiacol, provided by the invention, is prepared from the following raw materials: a 4-propyl guaiacol epoxy monomer and a curing agent; the curing agent contains amino groups and / or disulfide bonds. The bio-based epoxy resin based on 4-propyl guaiacol provided by the invention has the characteristic of being capable of being reprocessed for multiple times, and can keep the integrity of a chemical structure and the stability of thermodynamic properties after being reprocessed for multiple times. The bio-based epoxy resin based on the 4-propyl guaiacol can complete repair of surface scratches under the action of small pressure, can be chemically degraded easily in an N, N-dimethylformamide-solvent system, is convenient to degrade and recycle, and reduces pollution and damage to the ecological environment.

Description

Technical Field

[0001] The invention belongs to the technical field of epoxy resins and relates to a bio-based epoxy resin based on 4-propylguaiacol and a preparation method, a degradation method, a reprocessing method and an application thereof. Background Art

[0002] Epoxy resin is a polymer material containing two or more epoxy groups in its molecular structure. Compared with other thermosetting plastics, epoxy resin has better chemical and mechanical stability and can be made into a variety of materials such as packaging materials, coatings, injection molding materials, adhesives, etc., and is widely used in daily life and various fields of the national economy. There are many types of epoxy resins, among which bisphenol A epoxy resin (DGEBA) can be mass-produced due to its simple synthesis process, and its output accounts for more than 85% of the total epoxy resin.

[0003] Bisphenol A (BPA), the main raw material of the most widely used DGEBA, is mainly derived from petroleum. With the increasingly serious problem of oil depletion in recent years, humans have to redevelop green, environmentally friendly and sustainable biomass-based materials in order to replace non-renewable fossil resources and alleviate the problem of oil shortage. In addition, BPA, as an endocrine disruptor, can cause endocrine disorders and seriously threaten human health. In actual application, epoxy resin needs to undergo a curing and cross-linking reaction with a curing agent to form a polymer material containing a three-dimensional cross-linked network, which can only be applied to related fields after being processed and formed. However, although this curing and cross-linking reaction can improve the mechanical strength and physical and chemical stability of epoxy resin materials, once they are damaged or worn, they are difficult to repair, which reduces their service life. Therefore, the preparation of repairable epoxy materials that can be reprocessed and recycled has been a research focus in recent years. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a bio-based epoxy resin based on 4-propylguaiacol and a preparation method, a degradation method, a reprocessing method and an application thereof. The bio-based epoxy resin based on 4-propylguaiacol provided by the present invention has excellent repairability and reprocessing and recycling performance.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a bio-based epoxy resin based on 4-propylguaiacol, wherein the raw materials for preparation include a guaiacol-based epoxy monomer having a structure shown in Formula I and a curing agent;

[0007]

[0008] The curing agent contains amino groups and / or disulfide bonds.

[0009] Preferably, the curing agent is one or more of an amino-containing curing agent, a disulfide bond-containing curing agent, and an amino-disulfide bond-containing curing agent;

[0010] The amino-containing curing agent includes 4,4'-diaminodiphenylmethane and / or 4,4'-diaminodiphenyl sulfone;

[0011] The disulfide bond-containing curing agent includes one or more of dimethyl 3,3'-dithiodipropionate, dithiosalicylic acid and 3,3-dithiodipropionic acid;

[0012] The amino-disulfide bond-containing curing agent includes 4-aminophenyl disulfide;

[0013] The molar ratio of the guaiacol-based epoxy monomer to the curing agent is 1:0.5-2.

[0014] The present invention also provides a method for preparing the bio-based epoxy resin based on 4-propylguaiacol described in the above technical solution, comprising the following steps: mixing a guaiacol-based epoxy monomer and a curing agent, and curing to obtain the bio-based epoxy resin based on 4-propylguaiacol.

[0015] Preferably, the curing comprises sequentially performing a first curing and a second curing;

[0016] The first curing temperature is 90 to 150° C. and the time is 4 to 24 hours;

[0017] The second curing temperature is 160-200° C. and the time is 2-24 hours.

[0018] The present invention also provides a method for degrading a bio-based epoxy resin based on 4-propylguaiacol, comprising the following steps:

[0019] Placing a 4-propylguaiacol-based bio-based epoxy resin in a degradation solution for degradation to obtain a degradation product of the 4-propylguaiacol-based bio-based epoxy resin; the 4-propylguaiacol-based bio-based epoxy resin is the 4-propylguaiacol-based bio-based epoxy resin described in the above technical solution or the 4-propylguaiacol-based bio-based epoxy resin obtained by the preparation method described in the above technical solution;

[0020] The degradation liquid includes a polar solvent; the polar solvent includes one or more of an amide solvent, a furan solvent, a pyrrolidone solvent and a nitrile solvent.

[0021] Preferably, the volume concentration of the polar solvent in the degradation solution is 30 to 100%;

[0022] The degradation liquid further comprises a thiol-containing substance, wherein the thiol-containing substance comprises at least one of β-mercaptoethanol and dithiothreitol;

[0023] The degradation temperature is 20-100° C. and the degradation time is 0.5-144 hours.

[0024] The present invention also provides a degradation product of a bio-based epoxy resin based on 4-propylguaiacol prepared by the degradation method described in the above technical solution.

[0025] The present invention also provides a method for reprocessing a bio-based epoxy resin based on 4-propylguaiacol, comprising the following steps:

[0026] Reprocessing the 4-propylguaiacol-based bio-based epoxy resin to obtain a reprocessed 4-propylguaiacol-based bio-based epoxy resin; the 4-propylguaiacol-based bio-based epoxy resin is the 4-propylguaiacol-based bio-based epoxy resin described in the above technical solution or the 4-propylguaiacol-based bio-based epoxy resin prepared by the preparation method described in the above technical solution;

[0027] The reprocessing temperature is 140-200° C., the pressure is 1-15 MPa, and the time is 0.1-2 h.

[0028] The present invention also provides a reprocessed product of a bio-based epoxy resin based on 4-propylguaiacol prepared by the reprocessing method described in the above technical solution.

[0029] The present invention also provides the use of the 4-propylguaiacol-based bio-based epoxy resin described in the above technical solution, the 4-propylguaiacol-based bio-based epoxy resin prepared by the preparation method described in the above technical solution, the degradation product of the 4-propylguaiacol-based bio-based epoxy resin described in the above technical solution, or the reprocessed product of the 4-propylguaiacol-based bio-based epoxy resin described in the above technical solution in epoxy resin thermosetting materials.

[0030] The bio-based epoxy resin based on 4-propyl guaiacol provided by the present invention introduces a dynamic covalent bond through a curing agent, so that the bio-based epoxy resin based on 4-propyl guaiacol can self-repair well after being damaged, and has excellent self-repair properties for surface damage. The curing agent reacts with the guaiacol-based epoxy monomer to form a cross-linked structure, so that the bio-based epoxy resin based on 4-propyl guaiacol can be reprocessed, and after multiple reprocessing treatments, the chemical structure can still be kept intact and the thermodynamic properties can be kept stable, and it has excellent multiple cycle remodeling capabilities.

[0031] Moreover, the bio-based epoxy resin based on 4-propylguaiacol provided by the present invention can be easily chemically degraded in an N,N-dimethylformamide-solvent system, is easy to degrade and recycle, reduces pollution and damage to the ecological environment, and can replace commercial epoxy resins with bisphenol A toxicity in the fields of epoxy resin thermosetting materials.

[0032] The method for preparing the bio-based epoxy resin based on 4-propylguaiacol provided by the invention has simple process, simple operation, low production cost, is green and environmentally friendly, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The hydrogen nuclear magnetic resonance spectrum of the guaiacol-based epoxy monomer (BDEF) prepared in Example 1;

[0034] Figure 2 Infrared spectra of the guaiacol-based epoxy monomer (BDEF), guaiacol-based epoxy monomer (BDEF-EP), and 4-propylguaiacol-based bio-based epoxy resin (BDEF-EP-AFD) prepared in Example 1;

[0035] Figure 3 is the hydrogen nuclear magnetic resonance spectrum of the guaiacol-based epoxy monomer prepared in Example 1;

[0036] Figure 4 The Fourier transform infrared spectrum of the bio-based epoxy resin based on 4-propylguaiacol prepared in Example 1 after being reprocessed 0 to 4 times (R0 to R5);

[0037] Figure 5 This is a dynamic thermomechanical (DMA) test diagram of the 4-propylguaiacol-based bio-based epoxy resin prepared in Example 1 after being reprocessed 0 to 4 times (R0 to R5);

[0038] Figure 6 This is a diagram showing the degradation effect of the 4-propylguaiacol-based bio-based epoxy resin prepared in Example 1. DETAILED DESCRIPTION

[0039] The present invention provides a bio-based epoxy resin based on 4-propylguaiacol, wherein the raw materials for preparation include a guaiacol-based epoxy monomer having a structure shown in Formula I and a curing agent;

[0040]

[0041] The curing agent contains amino groups and / or disulfide bonds.

[0042] In the present invention, the guaiacol-based epoxy monomer is bis(4-methoxy-5-(oxiran-2-ylmethoxy)-2-propylphenyl)methane (abbreviated as BDEF-EP).

[0043] In the present invention, the curing agent is preferably one or more of an amino-containing curing agent, a disulfide bond-containing curing agent and an amino-disulfide bond-containing curing agent, and more preferably a mixture of an amino-containing curing agent and a disulfide bond-containing curing agent, or an amino-disulfide bond-containing curing agent; the molar ratio of the amino-containing curing agent and the disulfide bond-containing curing agent in the mixture of the amino-containing curing agent and the disulfide bond-containing curing agent is preferably 1 to 4:1, and in specific embodiments, it can be 1:1, 1:2, 1:3 or 1:4. In the present invention, the amino-containing curing agent preferably includes 4,4'-diaminodiphenylmethane and / or 4,4'-diaminodiphenyl sulfone. In the present invention, the disulfide bond-containing curing agent preferably includes one or more of 3,3'-dithiodipropionic acid dimethyl ester, dithiosalicylic acid and 3,3-dithiodipropionic acid. In the present invention, the amino-disulfide bond-containing curing agent preferably includes 4-aminophenyl disulfide (AFD).

[0044] In the present invention, the molar ratio of the guaiacol-based epoxy monomer to the curing agent is preferably 1:0.5-2, and in specific embodiments may be 1:0.5, 1:1, 1:1.5 or 1:2.

[0045] The bio-based epoxy resin based on 4-propyl guaiacol provided by the present invention introduces a dynamic covalent bond through a curing agent, so that the bio-based epoxy resin based on 4-propyl guaiacol can be well self-repaired after being damaged, and has excellent self-repairing properties for surface damage. The curing agent reacts with the guaiacol-based epoxy monomer to form a cross-linked structure, so that the bio-based epoxy resin based on 4-propyl guaiacol can be reprocessed, and after multiple reprocessing treatments, the chemical structure can still be kept intact and the thermodynamic properties can be kept stable, and it has excellent multiple cycle remodeling capabilities.

[0046] Moreover, the bio-based epoxy resin based on 4-propylguaiacol provided by the present invention can be easily chemically degraded in an N,N-dimethylformamide-solvent system, reducing the pollution and damage to the ecological environment, and can replace the commercial bisphenol A epoxy resin with certain toxicity in the fields of epoxy resin thermosetting materials (especially environmentally friendly epoxy resin thermosetting materials).

[0047] The present invention also provides a method for preparing the bio-based epoxy resin based on 4-propylguaiacol described in the above technical solution, comprising the following steps: mixing a guaiacol-based epoxy monomer and a curing agent, and curing to obtain the bio-based epoxy resin based on 4-propylguaiacol.

[0048] In the present invention, unless otherwise specified, the raw materials used in the present invention are preferably commercially available products.

[0049] In the present invention, the type of the curing agent and the molar ratio of the guaiacol-based epoxy monomer to the curing agent are preferably consistent with the above technical solution, which will not be described in detail herein.

[0050] In the present invention, the mixing preferably comprises: melting the guaiacol-based epoxy monomer, then adding a curing agent to stir and mix, and then vacuum degassing. In the present invention, the melting temperature is preferably 100-150°C, and in specific embodiments, it can be 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C or 150°C. In the present invention, the stirring and mixing time is preferably 10-40 minutes, and in specific embodiments, it can be 10 minutes, 20 minutes, 30 minutes or 40 minutes.

[0051] After the mixing is completed, the present invention preferably further comprises vacuum degassing the mixed solution obtained by the mixing, and then performing subsequent curing. In the present invention, the temperature of the vacuum degassing is preferably 70 to 100°C, and in specific embodiments it can be 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C; the time of the vacuum degassing is preferably 30 to 60 minutes, and in specific embodiments it can be 30 minutes, 40 minutes, 50 minutes or 60 minutes; the vacuum degassing is preferably carried out in an oven.

[0052] In the present invention, the curing preferably includes sequentially performing a first curing and a second curing. In the present invention, the temperature of the first curing is preferably 90 to 150°C, and in a specific embodiment, it can be 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C or 150°C; the time of the first curing is preferably 4 to 24h, and in a specific embodiment, it can be 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h or 24h. In the present invention, the temperature of the second curing is preferably 160-200°C, and in specific embodiments may be 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 190°C, 195°C or 200°C; the time of the second curing is preferably 2-24h, and in specific embodiments may be 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h or 24h.

[0053] In the present invention, the curing agent is 4-aminophenyl disulfide (AFD) as an example, and the curing mechanism is as follows:

[0054]

[0055] In the present invention, the preparation method of the guaiacol-based epoxy monomer preferably comprises the following steps:

[0056] Mixing 4-propylguaiacol, formaldehyde and phosphoric acid to carry out an electrophilic substitution reaction to obtain a guaiacol-based bisphenol monomer;

[0057] The guaiacol-based bisphenol monomer, a phase transfer catalyst and epichlorohydrin are mixed to perform a ring-opening reaction to obtain a ring-opening reaction system;

[0058] The ring-opening reaction system, a benzene solvent and an alkali metal hydroxide are mixed to carry out a ring-closing reaction to obtain a guaiacol-based epoxy monomer having a structure shown in formula I.

[0059] The invention mixes 4-propylguaiacol, formaldehyde and phosphoric acid, and performs an electrophilic substitution reaction to obtain a guaiacol-based bisphenol monomer.

[0060] In the present invention, the molar ratio of 4-propylguaiacol to phosphoric acid is preferably 1:0.1-0.8, and in specific embodiments, it can be 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7 or 1:0.8. In the present invention, the phosphoric acid is preferably used in the form of an aqueous phosphoric acid solution, and the mass concentration of the aqueous phosphoric acid solution is preferably 40-90%, and in specific embodiments, it can be 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85% or 90%.

[0061] In the present invention, the molar ratio of 4-propylguaiacol to formaldehyde is preferably 1:0.1-0.7, and in specific embodiments, it can be 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6 or 1:0.7. In the present invention, the formaldehyde is preferably used in the form of a formaldehyde aqueous solution, and the mass concentration of the formaldehyde aqueous solution is preferably 5-60%, and in specific embodiments, it can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 37%, 40%, 45%, 50%, 55% or 60%.

[0062] In the present invention, the mixing of 4-propylguaiacol, formaldehyde and phosphoric acid preferably comprises: first mixing 4-propylguaiacol and phosphoric acid, and then adding formaldehyde. In the present invention, the temperature of the first mixing is preferably 30 to 70°C, and in a specific embodiment, it can be 30°C, 40°C, 50°C, 60°C, 70°C or 80°C; the time of the first mixing is preferably 0.5 to 2h, and in a specific embodiment, it can be 0.5h, 1h, 1.5h or 2h. In the present invention, the formaldehyde is preferably added dropwise. In the present invention, the mixing is preferably carried out under stirring.

[0063] In the present invention, the temperature of the electrophilic substitution reaction is preferably 80-100°C, and in specific embodiments it can be 80°C, 85°C, 90°C, 95°C or 100°C; the time of the electrophilic substitution reaction is preferably 4-8h, and in specific embodiments it can be 4h, 5h, 6h, 7h or 8h; the time of the electrophilic substitution reaction is preferably started after the addition of formaldehyde is completed.

[0064] After the electrophilic substitution reaction is completed, the present invention preferably further comprises: washing the obtained electrophilic substitution reaction liquid with water, purifying it by column chromatography and drying it in sequence to obtain guaiacol-based bisphenol monomer. In the present invention, the water used for the water washing is preferably deionized water. The present invention has no special restrictions on the number of water washings and the amount of water used. The water washing is performed until the pH value of the obtained water washing liquid is neutral. In the present invention, the eluent used for the column chromatography purification preferably includes petroleum ether-ethyl acetate, chloroform-methanol or cyclohexane-acetonitrile; the volume ratio of petroleum ether and ethyl acetate in the petroleum ether-ethyl acetate is preferably 4 to 1:1, and in a specific embodiment, it can be 1:1, 2:1, 3:1 or 4:1; the volume ratio of chloroform and methanol in the chloroform-methanol is preferably 2 to 3:1, and in a specific embodiment, it can be 2:1, 2.5:1 or 3:1; the volume ratio of cyclohexane and acetonitrile in the cyclohexane-acetonitrile is preferably 2 to 3:1, and in a specific embodiment, it can be 2:1, 2.5:1 or 3:1. In the present invention, the drying temperature is preferably 50-80°C, and in specific embodiments, it can be 50°C, 60°C, 70°C or 80°C; the drying time is preferably 12-36h, and in specific embodiments, it can be 12h, 15h, 20h, 24h, 25h, 30h or 36h. In the present invention, the guaiacol-based bisphenol monomer is 5,5'-methylenebis(2-methoxy-4-propylphenol) (BDEF).

[0065] In the present invention, the mechanism of the electrophilic substitution reaction is as follows:

[0066]

[0067] After obtaining the guaiacol-based bisphenol monomer, the present invention mixes the guaiacol-based bisphenol monomer, a phase transfer catalyst and epichlorohydrin to perform a ring-opening reaction to obtain a ring-opening reaction system.

[0068] In the present invention, the phase transfer catalyst preferably includes one or more of organic ammonium halide, organic ammonium hydrogen sulfate, pyridine and organic amine; the organic ammonium halide preferably includes one or more of tetrabutylammonium bromide, tetrabutylammonium chloride, benzyltriethylammonium chloride, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride and tetradecyltrimethylammonium chloride; the organic ammonium hydrogen sulfate preferably includes tetrabutylammonium hydrogen sulfate; the organic amine preferably includes tributylamine. In the present invention, the molar ratio of the guaiacol-based bisphenol monomer to the phase transfer catalyst is preferably 1:0.001-0.02, and in specific embodiments it can be 1:0.001, 1:0.005, 1:0.008, 1:0.01, 1:0.015 or 1:0.02.

[0069] In the present invention, the molar ratio of the guaiacol-based bisphenol monomer to epichlorohydrin is preferably 1:10-20, and in specific embodiments may be 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19 or 1:20.

[0070] In the present invention, the temperature of the ring-opening reaction is preferably 80-100°C, and in specific embodiments it can be 80°C, 85, 90°C, 95°C or 100°C; the time of the ring-opening reaction is preferably 4-8h, and in specific embodiments it can be 4h, 5h, 6h, 7h or 8h.

[0071] After the ring-opening reaction is completed, the present invention preferably further comprises: distilling off the epichlorohydrin in the obtained ring-opening reaction liquid to obtain a ring-opening reaction system; the present invention has no special limitation on the distilling off operation, and the epichlorohydrin can be completely distilled off.

[0072] After obtaining the ring-opening reaction system, the present invention mixes the ring-opening reaction system, a benzene solvent and an alkali metal hydroxide to carry out a ring-closing reaction to obtain a guaiacol-based epoxy monomer having a structure shown in formula I.

[0073] In the present invention, the molar ratio of the guaiacol-based bisphenol monomer to the alkali metal hydroxide is preferably 1:0.1-0.9, and in specific embodiments, it can be 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.72, 1:0.8 or 1:0.9. In the present invention, the alkali metal hydroxide preferably includes at least one of sodium hydroxide and potassium hydroxide. In the present invention, the alkali metal hydroxide is preferably used in the form of an alkali metal hydroxide aqueous solution, and the mass concentration of the alkali metal hydroxide aqueous solution is preferably 30-50%, and in specific embodiments, it can be 30%, 35%, 40%, 45% or 50%.

[0074] In the present invention, the molar ratio of the guaiacol-based bisphenol monomer to the benzene solvent is preferably 1:10-20, and in specific embodiments may be 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19 or 1:20. In the present invention, the benzene solvent preferably includes one or more of toluene, xylene and ethylbenzene.

[0075] In the present invention, the temperature of the ring-closing reaction is preferably 80-100°C, and in specific embodiments it can be 80°C, 85, 90°C, 95°C or 100°C; the time of the ring-closing reaction is preferably 2-6h, and in specific embodiments it can be 2h, 3h, 4h, 5h or 6h.

[0076] In the present invention, the mechanism of the ring-opening reaction and the ring-closing reaction is as follows:

[0077]

[0078] After the ring-closure reaction is completed, the present invention preferably further comprises: washing the obtained ring-closure reaction liquid with water, distilling under reduced pressure, drying and purifying by column chromatography in sequence to obtain a guaiacol-based epoxy monomer. In the present invention, the water used for the water washing is preferably deionized water, and the present invention has no special restrictions on the number of times of the water washing and the amount of water used, as long as the excess reaction raw materials can be removed. The present invention has no special restrictions on the parameters of the distillation under reduced pressure and drying, as long as water and toluene can be removed. In the present invention, the eluent used for the column chromatography purification preferably includes petroleum ether-ethyl acetate or chloroform-methanol; the volume ratio of petroleum ether and ethyl acetate in the petroleum ether-ethyl acetate is preferably 1 to 4:1, and in specific embodiments, it can be 1:1, 2:1, 3:1 or 4:1; the volume ratio of chloroform and methanol in the chloroform-methanol is preferably 2 to 3:1, and in specific embodiments, it can be 2:1, 2.5:1 or 3:1.

[0079] The present invention also provides a method for degrading a bio-based epoxy resin based on 4-propylguaiacol, comprising the following steps: placing the bio-based epoxy resin based on 4-propylguaiacol in a degradation liquid for degradation to obtain a degradation product of the bio-based epoxy resin based on 4-propylguaiacol; the bio-based epoxy resin based on 4-propylguaiacol is the bio-based epoxy resin based on 4-propylguaiacol described in the above technical solution or the bio-based epoxy resin based on 4-propylguaiacol prepared by the preparation method described in the above technical solution.

[0080] In the present invention, the degradation liquid includes a polar solvent; the polar solvent includes one or more of an amide solvent, a furan solvent, a pyrrolidone solvent and a nitrile solvent, and more preferably includes one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide, tetrahydrofuran, N-methylpyrrolidone and acetonitrile. In the present invention, the volume concentration of the polar solvent in the degradation liquid is preferably 30-100%, and in a specific embodiment it can be 30%, 40%, 50%, 60%, 70%, 80%, 90% or 100%. In the present invention, the degradation liquid preferably also includes a thiol-containing substance, and the thiol-containing substance preferably includes at least one of β-mercaptoethanol (β-ME) and dithiothreitol.

[0081] In the present invention, the ratio of the mass of the bio-based epoxy resin based on 4-propylguaiacol to the volume of the degradation liquid is preferably 1g:10-30mL, and in specific embodiments, it can be 1g:10mL, 1g:15mL, 1g:20mL, 1g:25mL or 1g:30mL. In the present invention, the bio-based epoxy resin based on 4-propylguaiacol is preferably crushed and sieved in sequence before degradation; the sieve size of the sieve is preferably 80 mesh, and the part under the sieve is taken for subsequent degradation.

[0082] In the present invention, the degradation temperature is 20-100°C, and in specific embodiments it can be 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C or 100°C; the degradation time is preferably 0.5-144h, and in specific embodiments it can be 0.5h, 1h, 5h, 10h, 20h, 30h, 40h, 5h, 60h, 70h, 80h, 90h, 100h, 110h, 120h, 130h, 140h or 144h.

[0083] The present invention also provides a degradation product of a bio-based epoxy resin based on 4-propylguaiacol prepared by the degradation method described in the above technical solution.

[0084] The present invention also provides a method for reprocessing a bio-based epoxy resin based on 4-propylguaiacol, comprising the following steps: reprocessing the bio-based epoxy resin based on 4-propylguaiacol to obtain a reprocessed product of the bio-based epoxy resin based on 4-propylguaiacol.

[0085] In the present invention, the reprocessing temperature is preferably 140-180°C, and in specific embodiments it can be 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C or 180°C; the reprocessing pressure is 1-15MPa, and in specific embodiments it can be 1MPa, 2MPa, 3MPa, 4MPa, 5MPa, 6MPa, 7MPa, 8MPa, 9MPa, 10MPa, 11MPa, 12MPa, 13MPa, 14MPa or 15MPa; the number of reprocessing is preferably 1-5 times, and in specific embodiments it can be 1 time, 2 times, 3 times, 4 times or 5 times; the single reprocessing time is 0.1-2h, and in specific embodiments it can be 0.1h, 0.5h, 1h, 1.5h or 2h.

[0086] The present invention also provides a reprocessed product of a bio-based epoxy resin based on 4-propylguaiacol prepared by the reprocessing method described in the above technical solution.

[0087] The present invention also provides the use of the bio-based epoxy resin based on 4-propylguaiacol described in the above technical solution, the bio-based epoxy resin based on 4-propylguaiacol prepared by the preparation method described in the above technical solution, the degradation product of the bio-based epoxy resin based on 4-propylguaiacol described in the above technical solution, or the reprocessed product of the bio-based epoxy resin based on 4-propylguaiacol described in the above technical solution in epoxy resin thermosetting materials. The bio-based epoxy resin based on 4-propylguaiacol provided by the present invention has the characteristics of being able to be reprocessed multiple times, and can maintain the integrity of the chemical structure and the stability of the thermodynamic properties after multiple reprocessing. The bio-based epoxy resin based on 4-propylguaiacol can complete the repair of surface scratches under a small pressure, and can be easily chemically degraded in an N,N-dimethylformamide-solvent system, which is convenient for degradation and recycling, and reduces pollution and damage to the ecological environment. The bio-based epoxy resin based on 4-propylguaiacol and its reprocessed products and degradation products can be used to prepare epoxy resin thermosetting materials, especially to prepare environmentally friendly epoxy resin thermosetting materials.

[0088] The following is a detailed description of the 4-propylguaiacol-based bio-based epoxy resin provided by the present invention, as well as its preparation method, degradation method, reprocessing method and application, in conjunction with the embodiments. However, they should not be construed as limiting the scope of protection of the present invention.

[0089] Example 1

[0090] Preparation of guaiacol-based bisphenol monomer: 4-propyl guaiacol (0.22 mol) and phosphoric acid (mass concentration of 85%, 0.11 mol) were added and stirred at 50°C for 30 minutes, and 0.1 mol of formaldehyde aqueous solution (mass concentration of 37%) was added dropwise. After the addition was completed, the temperature was raised to 90°C for 6 hours to obtain a light reddish brown product, which was washed with deionized water until the washing liquid was neutral, concentrated, purified by column chromatography (eluent was petroleum ether: ethyl acetate volume ratio = 2:1), and dried at 60°C for 12 hours to obtain guaiacol-based bisphenol monomer (BDEF, white crystals, 34.1 g, yield 89%). The nuclear magnetic hydrogen spectrum of BDEF is as follows Figure 1 As shown in FIG. 1 , it can be seen that the present invention successfully prepared guaiacol-based bisphenol monomer. The infrared spectrum of BDEF is shown in FIG. Figure 2 As shown, we can see that 3265cm -1 The peak is attributed to the characteristic absorption peak of hydroxyl group in BDEF.

[0091] Preparation of guaiacol-based epoxy monomer: Add 0.05 mol of BDEF, 1 mol of epichlorohydrin and 0.0004 mol of tetrabutylammonium bromide at room temperature and under stirring, mix well, heat to 90°C for reaction for 6 hours, and remove excess epichlorohydrin in the system by vacuum distillation. After the epichlorohydrin is completely removed, add 0.95 mol of toluene and aqueous sodium hydroxide solution (mass concentration of 30%, 0.036 mol), heat to 90°C and continue to react for 3 hours, cool to room temperature, wash with deionized water, remove toluene by vacuum distillation, dry at 60°C, and purify by column chromatography (eluent is petroleum ether: ethyl acetate volume ratio = 2:1) to obtain guaiacol-based epoxy monomer (BDEF-EP, white crystals, 32.7 g, yield 86%). The nuclear magnetic hydrogen spectrum of BDEF-EP is shown as follows Figure 3 As shown, it can be seen that the present invention successfully prepared guaiacol-based epoxy monomers. The infrared spectrum of BDEF-EP is shown in Figure 2 As shown, it can be seen that 3265cm -1 The characteristic peak at 910cm- -1 A characteristic absorption peak attributed to the epoxy group in BDEF-EP appeared.

[0092] Preparation of bio-based epoxy resin based on 4-propyl guaiacol: melt the guaiacol-based epoxy monomer at 100°C, add 4-aminophenyl disulfide and stir for 10 minutes to mix evenly; then vacuum degas in a vacuum oven at 80°C for 30 minutes, pour into a mold, first cure at 120°C for 2 hours, and then second cure at 150°C for 2.5 hours to obtain a bio-based epoxy resin based on 4-propyl guaiacol (BDEF-EP-AFD). The infrared spectrum of BDEF-EP-AFD is shown in Figure 2 As shown in the figure, it can be seen that compared with the epoxy monomer BDEF-EP, the -1 The absorption peak of the epoxy group at the position disappears, and the characteristic absorption peak of CN (1270cm -1 ), indicating that the ring-opening reaction of the epoxy group occurred, and the characteristic absorption peak belonging to the benzene ring skeleton was observed to be stable and unchanged. The epoxy resin obtained by the final curing was at 910cm -1 The absorption peak of the epoxy group at completely disappeared, indicating that the epoxy ring-opening reaction was completely carried out.

[0093] Example 2

[0094] Multiple reprocessing of bio-based epoxy resins based on 4-propylguaiacol

[0095] The 4-propylguaiacol-based bio-based epoxy resin (denoted as R0) obtained in Example 1 was completely crushed into powder, and then placed in a hot press and reprocessed for 30 minutes at 180° C. and 10 MPa. The number of reprocessing was 4 times, and the reprocessed products of the 4-propylguaiacol-based bio-based epoxy resin were sequentially denoted as R1 (reprocessed once), R2 (reprocessed twice), R3 (reprocessed three times) and R4 (reprocessed four times).

[0096] The Fourier transform infrared spectra of R0~R5 are shown in Figure 4 The results showed that after multiple reprocessing cycles, the reprocessed product (remolded product) of the bio-based epoxy resin based on 4-propylguaiacol appeared a 1270 cm -1 CN at 3300cm -1 In addition, the characteristic absorption peak of -OH at about 1500cm -1 The characteristic CH peak at 2900 cm-1 and the methyl and methylene peaks at 2900 cm-1 -1 The characteristic CH peaks at the positions did not change, which indicated that BDEF-EP-AFD had good chemical structure stability after multiple reprocessing.

[0097] The DMA test analysis results of R0~R5 are shown in Figure 5, it can be seen that with the increase of the number of reprocessing, the storage modulus of BDEF-EP-AFD increases slightly and then tends to stabilize. The reprocessed product of 4-propylguaiacol-based bio-based epoxy resin shows a similar rubber platform, indicating that the bio-based epoxy resin based on 4-propylguaiacol can still maintain the integrity of the chemical structure and the stability of the thermodynamic properties after 4 reprocessing. Although it can be reprocessed many times in theory, it is found in practical applications that the aging of the material leads to a decrease in performance. With the continuous upgrading of the reprocessing process, the defects caused by hot pressing continue to intensify, resulting in an increase in the internal stress concentration inside the reprocessed product of 4-propylguaiacol-based bio-based epoxy resin. Therefore, the glass transition temperature of the resin seems to decrease slightly after reshaping, and finally stabilizes in the range of 112-113 °C.

[0098] Example 3

[0099] Degradation of bio-based epoxy resin based on 4-propylguaiacol

[0100] The 4-propylguaiacol-based bio-based epoxy resin obtained in Example 1 was crushed and passed through an 80-mesh sieve. The sieve-bottom portion was used and immersed in a mixed solution of N,N-dimethylformamide:β-mercaptoethanol with a volume ratio of 1:1 and β-mercaptoethanol, respectively, and allowed to stand at room temperature for degradation. The degradation results of 0 h, 2 h, 4 h and 16 h were shown in FIG. Figure 6 The ratio of the mass of the bio-based epoxy resin based on 4-propylguaiacol to the volume of the degradation liquid is 1 g:20 mL.

[0101] BDEF-EP-AFD completely dissolves in N,N-dimethylformamide-β-mercaptoethanol degradation solution at room temperature to obtain a yellow clear solution. However, when degraded in a single solvent of β-mercaptoethanol, no obvious degradation behavior is shown, which indicates that the swelling of N,N-dimethylformamide plays an important role in the degradation of epoxy resin. The degradation results show that the synthesized BDEF-EP-AFD has a flexible propyl side chain added to the structure, which effectively reduces the intermolecular force of the epoxy cross-linked network in the N,N-dimethylformamide solvent. The above-mentioned epoxy resin degradation behavior shows that the bio-based epoxy resin based on 4-propylguaiacol provided by the present invention has a relatively fast degradation ability at room temperature.

[0102] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A bio-based epoxy resin based on 4-propylguaiacol, wherein the raw materials for preparation include a guaiacol-based epoxy monomer having a structure shown in Formula I and a curing agent; The curing agent contains amino groups and / or disulfide bonds.

2. The bio-based epoxy resin based on 4-propylguaiacol according to claim 1, characterized in that The curing agent is one or more of an amino-containing curing agent, a disulfide bond-containing curing agent, and an amino-disulfide bond-containing curing agent; The amino-containing curing agent includes 4,4'-diaminodiphenylmethane and / or 4,4'-diaminodiphenyl sulfone; The disulfide bond-containing curing agent includes one or more of dimethyl 3,3'-dithiodipropionate, dithiosalicylic acid and 3,3-dithiodipropionic acid; The amino-disulfide bond-containing curing agent includes 4-aminophenyl disulfide; The molar ratio of the guaiacol-based epoxy monomer to the curing agent is 1:0.5-2.

3. The method for preparing the bio-based epoxy resin based on 4-propylguaiacol according to claim 1 or 2, comprising the following steps: The guaiacol-based epoxy monomer and the curing agent are mixed and cured to obtain the 4-propylguaiacol-based bio-based epoxy resin.

4. The preparation method according to claim 3, characterized in that: The curing comprises sequentially performing a first curing and a second curing; The first curing temperature is 90 to 150° C. and the time is 4 to 24 hours; The second curing temperature is 160-200° C. and the time is 2-24 hours.

5. A method for degrading a bio-based epoxy resin based on 4-propylguaiacol, comprising the following steps: Placing a 4-propylguaiacol-based bio-based epoxy resin in a degradation solution for degradation to obtain a degradation product of the 4-propylguaiacol-based bio-based epoxy resin; the 4-propylguaiacol-based bio-based epoxy resin is the 4-propylguaiacol-based bio-based epoxy resin according to any one of claims 1 to 2 or the 4-propylguaiacol-based bio-based epoxy resin obtained by the preparation method according to any one of claims 3 to 4; The degradation liquid includes a polar solvent; the polar solvent includes one or more of an amide solvent, a furan solvent, a pyrrolidone solvent and a nitrile solvent.

6. The degradation method according to claim 5, characterized in that: The volume concentration of the polar solvent in the degradation solution is 30 to 100%; The degradation liquid further comprises a thiol-containing substance, wherein the thiol-containing substance comprises at least one of β-mercaptoethanol and dithiothreitol; The degradation temperature is 20-100° C. and the degradation time is 0.5-144 hours.

7. The degradation product of the bio-based epoxy resin based on 4-propylguaiacol obtained by the degradation method according to claim 5 or 6.

8. A method for reprocessing a bio-based epoxy resin based on 4-propylguaiacol, comprising the following steps: Reprocessing the 4-propylguaiacol-based bio-based epoxy resin to obtain a reprocessed 4-propylguaiacol-based bio-based epoxy resin; the 4-propylguaiacol-based bio-based epoxy resin is the 4-propylguaiacol-based bio-based epoxy resin according to any one of claims 1 to 2 or the 4-propylguaiacol-based bio-based epoxy resin obtained by the preparation method according to any one of claims 3 to 4; The reprocessing temperature is 140-200° C., the pressure is 1-15 MPa, and the time is 0.1-2 h.

9. The reprocessed product of the 4-propylguaiacol-based bio-based epoxy resin obtained by the reprocessing method of claim 8.

10. Use of the 4-propylguaiacol-based bio-based epoxy resin according to any one of claims 1 to 2, the 4-propylguaiacol-based bio-based epoxy resin prepared by the preparation method according to any one of claims 3 to 4, the degradation product of the 4-propylguaiacol-based bio-based epoxy resin according to claim 7, or the reprocessed product of the 4-propylguaiacol-based bio-based epoxy resin according to claim 9 in epoxy resin thermosetting materials.

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